Description
The sawfish's most distinctive feature is the saw-like rostrum. The rostrum is covered with sensitive pores that allow the sawfish to detect movement of prey hiding under the ocean floor. The rostrum serves as a digging tool to unearth buried crustaceans. When a suitable prey swims by, the normally lethargic sawfish springs from the bottom and slashes at it with its saw. This generally stuns or injures the prey sufficiently for the sawfish to devour it. Sawfish also defend themselves with their rostrum, against intruding divers and predators such as sharks. The "teeth" protruding from the rostrum are not real teeth, but modified tooth-like structures called denticles.
The body and head of a sawfish are flat, and they spend most of their time lying on the sea floor. Like rays, sawfish's mouth and nostrils are on their flat undersides. The mouth is lined with small, dome-shaped teeth for eating small fish and crustaceans; sometimes the fish swallows them whole. Sawfish breathe with two spiracles just behind the eyes that draw water to the gills. The skin is covered with tiny dermal denticles that gives the fish a rough texture. Sawfish are usually light grey or brown; the smalltooth sawfish, Pristis pectinata, appears olive green.
Like other elasmobranchs, sawfish lack a swim bladder and use a large, oil-filled liver to control buoyancy. Their skeleton is made of cartilage.
The eyes of the sawfish are undeveloped due to their muddy habitat. The rostrum is the main sensory device.
The intestines are shaped like a corkscrew, called a spiral-valve.
The smallest sawfish is the dwarf sawfish (P. clavata), which can be as long as 1.4 metres (4.6 ft), much smaller than the others. The largest species seem to be the largetooth sawfish (P. microdon), the Leichhardt's sawfish (P. perotteti), and the common sawfish (P. pristis), which all can reach approximately 7 m (23 ft) in length. One southern sawfish was recorded as weighing 2.455 tonnes (5,410 lb).
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